Abbe condenser

ABSTRACT

A two-component microscope condenser consisting of a biconvex positive doublet as the first component and a convex-plano positive doublet as the second component has excellent correction for spherical aberration and coma with significant reduction of pupillary aberration. The front pupil plane of the condenser is located external to the glass in order to provide utility of the condenser in microscope techniques requiring positioning of optical elements in the pupil plane. A negative lens may be combined with one embodiment of the invention to provide a longer working distance.

BACKGROUND OF THE INVENTION

This invention relates to Abbe condensers and more particularly toimproved Abbe condensers having excellent correction for sphericalaberration and coma with significant reduction in the usual pupillaryaberration.

Abbe condensers are well known and conventionally have a biconvex firstelement with a convex-plano second element. However, the first andsecond elements have been singlets except in the case of extremelycomplex condensers having a substantial number of additional componentsand usually having a triplet as the first element. Thus, microscopistseither had to be satisfied with amounts of spherical aberration andcoma, as well as pupillary aberration that were commonly present inconventional Abbe condensers or make a considerable investment for acomplex condenser system in order to perform microscopy techniqueshindered or prevented by conventional Abbe condensers.

It is an object of the present invention to provide an improved Abbecondenser.

It is another object of the present invention to provide an Abbecondenser having excellent correction for spherical aberration and comaand being well corrected for pupillary aberrations.

It is a further object of the present invention to provide an improvedAbbe condenser with significantly reduced axial color aberration.

It is a still further object of the present invention to provide an Abbecondenser consisting of a biconvex positive doublet and a convex-pianopositive doublet.

It is also another object of the present invention to provide animproved Abbe condenser of close working distance that can have theworking distance increased by a negative lens.

BRIEF DESCRIPTION OF THE PRESENT INVENTION AND DRAWINGS

Improved Abbe condensers have two components with the first componentbeing a biconvex positive doublet and the second component being aconvex-piano positive doublet. The improved condensers have excellentcorrection for spherical aberration and coma, as well as significantlyreduced pupillary aberration.

FIG. 1 is an optical diagram of one embodiment of the present invention;

FIG. 2 is an optical diagram of another embodiment of the presentinvention; and

FIG. 3 is an optical diagram of still another embodiment of the presentinvention.

DESCRIPTION OF THE EMBODIMENTS

The condenser, as shown in FIG. 1, has a numerical aperture ofapproximately 0.90, excellent correction for spherical aberration andcomma and significant reduction of pupillary aberration. Referring toFIG. 1, a biconvex positive doublet I consists of a biconvex singletcemented to a concavo-convex singlet and is the first element of thecondenser. A convex-plano positive doublet II is axially aligned withbiconvex positive doublet I and is the other component of the condensersystem.

The lens parameters of the two components are given in Table I with lensradii designated as R₁ to R₆, a minus sign (-) indicates the center ofcurvature on the pupil side of the lens, thicknesses are designated T₁to T₄, spacings are designated S₀ to S₂, indices of refraction aredesignated ND₁ to ND₄ and Abbe numbers are designated ν₁ to ν₄. X is avariable having a value of about 9 to 13mm.

                                      TABLE I                                     __________________________________________________________________________                             Index of  Abbe                                       Lens                                                                             Radius  Thickness                                                                            Spacing                                                                              Refraction                                                                              Number                                     __________________________________________________________________________                      S.sub.0 =0.3562X                                               R.sub.1 = 1.9558X                                                                     T.sub.1 =0.9662X                                                                            1.620<ND.sub.(1) <1.621                                                                 γ.sub.(1) ≅60               I R.sub.2 =-1.2632X                                                                     T.sub.2 =0.1905X                                                                            1.78<ND.sub.(2) <1.79                                                                   γ.sub.(2) ≅25                 R.sub.3 =-4.3594X                                                                            S.sub.1 =0.0095X                                               R.sub.4 = 0.8097X                                                                     T.sub.3 =0.7669X                                                                            1.66<ND.sub.(3) <1.67                                                                   γ.sub.(3) ≅42              II R.sub.5 =∞                                                                      T.sub.4 =0.3900X                                                                            1.78<ND.sub.(4) <1.79                                                                   γ.sub.(4) ≅25                 R.sub.6 =∞                                                                             S.sub.2 =0.0286X                                                       T.sub.5 =0.1190X                                                                            1.52<ND.sub.(5) <1.53                                                                   γ.sub.(5) ≅58              __________________________________________________________________________

T₅, ND₅ and ν₅, given in the above Table, are respresentative ofconventional microscope slides. While illustrated in the drawing anddefined in the Table, the slide does not form a part of the presentinvention. Those skilled in the art can easily adapt the condensersystem to a slide of unusual thickness or having an unusual index ofrefraction and Abbe number.

A preferred embodiment, where X=10.5mm, has the following values:

                  TABLE II                                                        ______________________________________                                                                       Index of Abbe                                  Lens Radius   Thickness Spacing                                                                              Refraction                                                                             Number                                ______________________________________                                                                S.sub.0 =3.74                                              R.sub.1 =                                                                      20.5357                                                                                T.sub.1 =10.145 ND.sub.1 =1.6203                                                                       γ.sub.1 =60.3                    I   R.sub.2 =                                                                     -13.2638                                                                               T.sub.2 =2.000   ND.sub.2 =1.78600                                                                      γ.sub.2 =25.5                        R.sub.3 =                                                                     -45.7739                                                                                         S.sub.1 =0.10                                              R.sub.4 =                                                                       8.5021                                                                               T.sub.3 =8.053   ND.sub.3 =1.66741                                                                      γ.sub.3 =41.9                   II   R.sub.5 =∞                                                                       T.sub.4 =4.095   ND.sub.4 =1.78600                                                                      γ.sub.4 =25.5                        R.sub.6 =∞                                                                                 S.sub.2 =0.30                                                       T.sub.5 =1.250   ND.sub.5 =1.5244                                                                       γ.sub.5 =58.3                   ______________________________________                                    

The embodiment of FIG. 2 has a biconvex positive doublet XI as the firstelement being composed of a biconvex singlet, the first surface of whichis an axially symmetrical aspherical surface and a concavo-convexsinglet cemented thereto. The second element is axially aligned with thebiconvex positive doublet XI and is a convex-plano positive doublet XIIcomposed of a convex-plano singlet cemented to a plano plate.

The lens parameters of the two components are given in Table III withlens radii designated as R₁₁ to R₁₆, a minus sign (-) indicates thecenter of curvature on the pupil side of the lens, thicknesses aredesignated T₁₁ to T₁₄ , spacings are designated S₁₀ to S₁₂, indices ofrefraction are designated ND₁₁ to ND₁₄ and Abbe numbers are designatedν₁₁ to ν₁₄.

                                      TABLE III                                   __________________________________________________________________________                             Index of  Abbe                                       Lens                                                                             Radius  Thickness                                                                            Spacing                                                                              Refraction                                                                              Number                                     __________________________________________________________________________                      S.sub.10 =0.2894X                                              R.sub.11 = 1.2120X                                                                    T.sub.11 =1.0311X                                                                           1.522<ND.sub.11 <1.524                                                                  γ.sub.11 ≅58                XI                                                                              R.sub.12 =-1.4414X                                                                    T.sub.12 =0.1905X                                                                           1.785<ND.sub.12 <1.787                                                                  γ.sub.12 ≅25                  R.sub.13 =-3.3477X                                                                           S.sub.11 =0.0095X                                              R.sub.14 = 0.7720X                                                                    T.sub.13 =0.4264X                                                                           1.619<ND.sub.13 <1.621                                                                  γ.sub.13 ≅60               XII                                                                              R.sub.15 =∞                                                                     T.sub.14 =0.5212X                                                                           1.785<ND.sub.14 <1.787                                                                  γ.sub.14 ≅25                  R.sub.16 =∞                                                                            S.sub.12 =0.0381X                                                       T.sub.5 =0.1190X                                                                           1.52<ND.sub.5 <1.53                                                                     γ.sub.5 ≅58                __________________________________________________________________________

wherein X is 9 to 13mm, the front surface of lens XI, with radius R₁₁,is an axially symmetrical aspheric surface with axis of rotation Z. Thevalue of Z, for any given value of x and y, is defined by the equation##EQU1## Wherein: d=0.380331·10⁻⁵

e=-0.428527·10⁻⁷

f=0.124135·10⁻⁸

g=-0.709653·10⁻¹¹

p² =x² + y²

c=1/R₁₁, and

k=-0.536389

An embodiment, where X is 10.5mm, has the following values:

                                      TABLE IV                                    __________________________________________________________________________                            Index of                                                                             Abbe                                           Lens                                                                              Radius  Thickness                                                                            Spacing                                                                            Refraction                                                                           Number                                         __________________________________________________________________________                       S.sub.10 =3.04                                                 *R.sub.11 = 12.727                                                                     T.sub.11 =10.826                                                                         ND.sub.11 =1.523                                                                     γ.sub.11 =58.6                            XXI                                                                              R.sub.12 =-15.135                                                                     T.sub.12 =2.000                                                                           ND.sub.12 =1.786                                                                     γ.sub.12 =25.5                               R.sub.13 =-35.151                                                                            S.sub.11 =0.10                                                 R.sub.14 =  8.107                                                                     T.sub.13 =4.477                                                                           ND.sub.13 =1.620                                                                     γ.sub.13 =60.3                           XXII                                                                              R.sub.15 =∞                                                                     T.sub.14 =5.473                                                                           ND.sub.14 =1.786                                                                     γ.sub.14 =25.5                               R.sub.16 =∞                                                                            S.sub.12 =0.40                                                         T.sub.5 =1.250                                                                            ND.sub.5 =1.5244                                                                     γ.sub.5 =58.3                            __________________________________________________________________________     *Aspheric surface having conic coefficient and four deformation               coefficients given in Table III.                                         

Another embodiment of the condenser according to FIG. 2 has thefollowing parameters:

                                      TABLE V                                     __________________________________________________________________________                              Index of                                                                              Abbe                                        Lens                                                                             Radius  Thickness                                                                             Spacing                                                                              Refraction                                                                            Number                                      __________________________________________________________________________                       S.sub.10 =0.163X                                              R.sub.11 = 1.261X      1.5<ND.sub.11 <1.6                                                                    γ.sub.11 ≅59                           T.sub.11 =1.085X                                                    XI                                                                              R.sub.12 =-1.385X                                                                     T.sub.12 =0.271X                                                                             1.7<ND.sub.12 <1.8                                                                    γ.sub.12 ≅25                   R.sub.13 =-2.891X                                                                             S.sub.11 =0.009X                                              R.sub.14 = 0.719X                                                                     T.sub.13 =0.414X                                                                             1.5<ND.sub.13 <1.6                                                                    γ.sub.13 ≅61                XII                                                                              R.sub.15 =∞                                                                      T.sub.14 =0.5423X                                                                           1.7<ND.sub.14 <1.8                                                                    γ.sub.14 ≅25                   R.sub.16 =∞                                                                             S.sub.12 =0.036X                                           __________________________________________________________________________

where X is 9 to 13mm and the conic coefficient and four deformationcoefficients are:

d=0.335486·10⁻⁵

e=-0.329104·10⁻⁷

f=0.70309·10⁻⁹

g=-0.349273·10⁻¹¹

p² =x² + y²

c=1/R₁₁, and

k=-0.556707

The preferred embodiment, where X is 11.4mm and has the followingvalues:

                  TABLE VI                                                        ______________________________________                                                                       Index of Abbe                                  Lens Radius   Thickness Spacing                                                                              Refraction                                                                             Number                                ______________________________________                                                                S.sub.10 =1.86                                             *R.sub.11 =                                                                    14.375                                                                                T.sub.11 =12.37  ND.sub.11 =1.523                                                                       γ.sub.11 =58.6                   XI  R.sub.12 =                                                                    -15.792                                                                                T.sub.12 =3.09   ND.sub.12 =1.786                                                                       γ.sub.12 =25.5                       R.sub.13 =                                                                    -32.960                                                                                          S.sub.11 =0.10                                             R.sub.14 =                                                                      8.194                                                                                T.sub.13 =4.72   ND.sub.13 =1.589                                                                       γ.sub.13 =61.2                  XII  R.sub.15 =∞                                                                      T.sub.14 =6.18   ND.sub.14 =1.786                                                                       γ.sub.14 =25.5                       R.sub.16 =∞                                                                                S.sub.12 =                                                                     0.411                                                ______________________________________                                         *Aspheric surface having conic coefficient and four deformation               coefficients given in Table V.                                           

Referring to FIG. 3, lenses XI and XII are the same as the correspondinglenses of FIG. 2. Lens XXI is a negative throwin lens which can beoptionally used with lenses XI and XII to increase the working distanceof the condenser.

The parameters of lens XXI are as follows:

R₂₁ is from about -250 to =500mm, R₂₂ is from about 62.0 to 23mm, T₂₁ isfrom about 3.2 to 4.0mm; S₂₁ is from about 4.2 to 5.4mm, ND₂₁ is fromabout 1.6 to 1.8 and ν₂₁ is about 31. The specific values of the aboveparameters are selected to provide the desired condenser workingdistance according to the formula ##EQU2## where f cond is the focallength of the condenser, working distance is the space S₂₂ and f neglens is the focal length of the appropriate negative lens. For thecondenser of Table VI having a focal length of 11.4, the value of f neglens may range from about -32.9 to -89.6 to provide an air workingdistance of about 5mm to 2.5mm. A preferred negative lens XXI has thefollowing values:

R₂₁ =∞

r₂₂ =39.779

t₂₁ =3.60

nd₂₁ =1.689

ν₂₁ =30.9

s₂₂ is then equal to about 3.3mm and S₂₁ is about 3mm. The space, S₂₁,is not critical and is preferably selected relative to the sag of thesurface with radius R₂₂ to provide sufficient clearance for an opticalelement, such as a phase annulus which is preferably located in or verynear the front focal plane, S₁₀, of the condenser.

What is claimed is:
 1. A two-component microscope condenser having aworking distance effective for either an air space or oil filled spaceand having a front pupil plane external to the glass thereof, saidcondenser consisting of a biconvex positive doublet and a convex-planopositive doublet aligned along an optical axis.
 2. The condenser ofclaim 1 wherein said biconvex doublet has an aspherical first surface.3. The condenser of claim 2 in which said two components have parametersof lens radii (R), a minus sign (-) indicates center of curvature on thepupil side of the lens, thicknesses (T), spacings (S), indices ofrefraction (ND) and Abbe numbers (ν) as follows:

    __________________________________________________________________________                             Index of  Abbe                                       Lens                                                                             Radius  Thickness                                                                            Spacing                                                                              Refraction                                                                              Number                                     __________________________________________________________________________                      S.sub.10 =0.2894X                                              R.sub.11 = 1.2120X                                                                    T.sub.11 =1.0311X                                                                           1.522<ND.sub.11 <1.524                                                                  γ.sub.11 ≅58               I  R.sub.12 =-1.4414X                                                                    T.sub.12 =0.1905X                                                                           1.785<ND.sub.12 <1.787                                                                  γ.sub.12 ≅25                  R.sub.13 =-3.3477X                                                                           S.sub.11 =0.0095X                                              R.sub.14 = 0.7720X                                                                    T.sub.13 =0.4264X                                                                           1.619<ND.sub.13 <1.621                                                                  γ.sub.13 ≅60               II R.sub.15 =∞                                                                     T.sub.14 =0.5212X                                                                           1.785<ND.sub.14 <1.787                                                                  γ.sub.14 ≅25                  R.sub.16 =∞                                                                            S.sub.12 =0.0381X                                           __________________________________________________________________________

wherein X is 9 to 13mm, the surface having radius R₁₁ is an axiallysymmetrical aspherical surface conforming to the equation ##EQU3## witha conic coefficient (k) of -0.536389 and deformation coefficients d of0.380331·10⁻⁵, e of -0.428527·10⁻⁷, f of 0.124135·10⁻⁸ and g of-0.709653·10⁻¹¹.
 4. The condenser of claim 3 wherein X is 10.5mm, ND₁₁is 1.523, ND₁₂ is 1.786, ND₁₃ is 1.620, ND₁₄ is 1.786, ν₁₁ is 58.6, ν₁₂is 25.5, ν₁₃ is 60.3 and ν₁₄ is 25.5.
 5. The condenser of claim 1 inwhich said two components have parameters of lens radii (R), a minussign (-) indicates center of curvature on the pupil side of the lens,thicknesses (T), spacings (S), indicates of refraction (ND) and Abbenumbers (ν) as follows:

    __________________________________________________________________________                             Index of  Abbe                                       Lens                                                                             Radius  Thickness                                                                            Spacing                                                                              Refraction                                                                              Number                                     __________________________________________________________________________                      S.sub.0 =0.3562X                                               R.sub.1 = 1.9558X                                                                     T.sub.1 =0.9662X                                                                            1.620<ND.sub.(1) <1.621                                                                 γ.sub.(1) ≅60               I R.sub.2 =-1.2632X                                                                     T.sub.2 =0.1905X                                                                            1.78<ND.sub.(2) <1.79                                                                   γ.sub.(2) ≅25                 R.sub.3 =-4.3594X                                                                            S.sub.1 =0.0095X                                               R.sub.4 = 0.8097X                                                                     T.sub.3 =0.7669X                                                                            1.66<ND.sub.(3) <1.67                                                                   γ.sub.(3) ≅42              II R.sub.5 = ∞                                                                     T.sub.4 =0.3900X                                                                            1.78<ND.sub.(4) <1.79                                                                   γ.sub.(4) ≅25                 R.sub.6 =∞                                                                             S.sub.2 =0.0286X                                            __________________________________________________________________________

wherein X is 9 to 13mm.
 6. The condenser of claim 5 wherein X is 10.5,ND₁ is 1.6203, ND₂ is 1.78600, ND₃ is 1.66741, ND₄ is 1.78600, ν₁ is60.3, ν₂ is 25.5, ν₃ is 41.9 and ν₄ is 25.5.
 7. The condenser of claim 2in which said two components have parameters of lens radii (R), a minussign (-) indicates center of curvature and the pupil side of the lens,thicknesses (T), spacings (S), indies of refraction (ND) and Abbenumbers (ν) as follows:

    __________________________________________________________________________                              Index of                                                                              Abbe                                        Lens                                                                             Radius  Thickness                                                                             Spacing                                                                              Refraction                                                                            Number                                      __________________________________________________________________________                       S.sub.10 =0.163X                                              R.sub.11 = 1.261X      1.5<ND.sub.11 <1.6                                                                    γ.sub.11 ≅59                           T.sub.11 =1.085X                                                    XI                                                                              R.sub.12 =-1.385X                                                                     T.sub.12 =0.271X                                                                             1.7<ND.sub.12 <1.8                                                                    γ.sub.12 ≅25                   R.sub.13 =-2.891X                                                                             S.sub.11 =0.009X                                              R.sub.14 = 0.719X                                                                     T.sub.13 =0.414X                                                                             1.5<ND.sub.13 <1.6                                                                    γ.sub.13 ≅61                XII                                                                              R.sub.15 =∞                                                                      T.sub.14 =0.5423X                                                                           1.7<ND.sub.14 <1.8                                                                    γ.sub.14 ≅25                   R.sub.16 =∞                                                                             S.sub.12 =0.036X                                           __________________________________________________________________________

wherein X is 9 to 13mm, the surface having radius R₁₁ is an axiallysymmetrical aspheric surface conforming to the equation ##EQU4## with aconic coefficient (k) of -0.556707, and deformation coefficients d of0.335486·10⁻⁵, e of -0.329104·10⁻⁷, f of 0.70309·10⁻⁹ and g of-0.349273·10⁻¹¹.
 8. The condenser of claim 7 wherein X is 11.4mm, ND₁₁is 1.523, ND₁₂ is 1.786, ND₁₃ is 1.589, ND₁₄ is 1.786, ν₁₁ is 58.6, ν₁₂is 25.5, ν₁₃ is 61.2 and ν₁₄ is 25.5.
 9. The condenser of claim 2further including a negative lens having a concave rear surfacepositioned near the front pupil plane of said condenser.
 10. Thecondenser of claim 9 wherein said negative lens has a focal length ofabout -32.9 to about -89.6.
 11. The condenser of claim 8 furtherincluding a plano-concave negative lens to provide an air workingdistance, S₂₂, of 2.5 to 5mm.
 12. The condenser of claim 11 wherein saidnegative lens has a concave radius, R₂₂, of 39.779mm, a thickness, T₂₁,of 3.60mm, an index of refraction, ND₂₁, of 1.689, an Abbe number, ν₂₁,of 30.9 and the working distance is about 3.3mm.